In the field of wireless communications a greater emphasis has always been put since the origin on the development of products and communications infrastructures offering higher data rates so that it was possible, e.g., to add sophisticated data services after the initial objective of transmitting voice over a digital wireless network was achieved. Following this trend, GSM (global system for mobile communications), the predominant world wide wireless telephone system, has constantly evolved to offer higher data rates. Starting from a low data rate of 9.6 kilobits per second (Kbps), the first generation of digital mobile phone (2G) only allowed the exchange of text messages in the form of SMS (short message service). It has since evolved to a third generation of products (3G), through intermediate development steps (2.5 & 2.75), offering higher data rates so that a mobile phone can now receive videos and connect to the Internet over a public wireless network. Typically, network are organized in geographic cells of sizes as low as a few hundreds meters in urban areas up to several kilometers (Km) in less densely populated areas (maximum 35 km).
Another area in the field of telecommunications that has later received a great deal of attention is the wireless interconnection of the countless number of electronic devices now part of almost any human activity. This includes the above cellular phones that can now connect, e.g., to a wireless headset and, in general, to any sort of device properly equipped such as a PDA (portable digital assistant), a laptop computer, etc. To this end, the definition and publication of specifications by the Bluetooth Special Interest Group (SIG) since 1998 has allowed the development, licensing and implementation of standard devices capable of actually interconnecting with each other's. Typically, Bluetooth devices are relatively low-power devices capable of interconnecting within a few-meter range at a data rate of one megabit per second (Mbps).
There is however another area in the field of wireless communications that has failed receiving the attention it would have deserved yet. The two above mentioned areas have actually in common the objective of providing a relatively large data rate (in the order of 1 Mbps) for the applications they support. Hence, they are not only able to transmit voice but have also a significant bandwidth available for all sorts of data applications. At this point of view, GSM and Bluetooth only differ in their ability to communicate at different distances; typically, within a few kilometers for a cellular phone and a few meters for a Bluetooth device.
Among the plethora of electronic devices which need to communicate with each other's, or with a central communications point, many have however to run applications that only require a modest data rate to operate satisfactorily, well below that required to transmit voice in a digital form. Typically, a few Kbps is enough in many applications, e.g., in telemetry and remote monitoring systems. In this kind of applications there is only the need to communicate, often at scheduled intervals, the status of a sensor aimed at measuring a parameter, e.g., the temperature of a room in a building.
Even though Bluetooth SIG has launched a ‘low energy’ initiative to further reduce, as the name suggests, the power required to operate Bluetooth devices, a strong requirement for the above type of applications, it fails however addressing another requirement which is the ability to communicate over larger distances than the ten meters retained by the Bluetooth low energy specification. Indeed, many of the applications addressed by the invention, like telemetry and remote monitoring, need practically to communicate over longer distances without having recourse to a relay which necessarily needs to be located in close proximity of the Bluetooth device.
Hence, it is an object of the invention to disclose a system capable of communicating over distances significantly greater than the ten meters of the Bluetooth low energy specification while maintaining an equivalent operating point as far as energy dissipation of the device, power of the transmitter, and sensibility of the receiver are concerned.
Further objects, features and advantages of the present invention will become apparent to the ones skilled in the art upon examination of the following description in reference to the accompanying drawings. It is intended that any additional advantages be incorporated herein.